Typically, swimming pools include a pump for drawing water from a drain at the bottom of a pool through a debris collection trap to a filter from which the water is returned to the pool. Most pools also include a skimmer in fluid communication with the debris collection trap. A typical debris collection trap of this type is illustrated and described in U.S. Pat. No. 5,265,631, which patent describes an invention by the present inventor and is assigned the present assignee.
The drain at the bottom of a swimming pool can pose a safety hazard to an occupant of the pool, particularly a young child or a person of limited physical strength. As water is drawn through the drain by the pump, a suction force exists at the surface of the drain. Should a user of a pool inadvertently cover the drain with a part of his/her body, the suction force will tend to retain the user against the drain unless the user has sufficient strength to push away from the drain. If such strength is not available or if the user panics, drowning may result. Furthermore, even if the user is capable of pushing away from the drain, injury of more or less seriousness may result.
To overcome the potential for injury or drowning due to being drawn against and retained by a swimming pool drain, various devices have been developed over the years to break the pump suction in the event a high suction condition is sensed due to covering or at least restricting the flow of water through the drain. Some of these devices introduce air to the inlet side of the pump in response to the sensed high suction condition, which results in loss of pump prime. Other devices interrupt the power source to the pump and the pump ceases to operate. There are also devices which provide for a conduit open to the atmosphere that is submerged a given distance below the pool water level and connected to the pump inlet to introduce air if a predetermined level of suction is sensed.
There are numerous problems attendant existing prior art devices, which problems will be summarized below. Many of the devices are very expensive and have many moving parts. Some of the devices provide false signals triggered by partly or wholly filled pump and/or skimmer baskets. Installation of some devices may require several feet of excavation for installation purposes which render them expensive and the resulting deterrent may preclude installation. Depending upon the system installed, the pump may be damaged upon actuation with the resulting attendant problems of expense and loss of use of the swimming pool.